I always feel striking that balance between routine and spontaneity is not hard, but when you get hit that certain note, it's the sweet spot to happiness or whatever is closest to the elusive 'feeling' humans ever strive for (not unlike 'love').
I am a creature of habit, I seek it out in many ways. There is a happiness in the repetition to me, but more on an overall scale, such as the repetition of the seasons, which are large scale patterns and within that, if a bit of spontaneity can exist, that seems to make things a bit more 'fun'.
Though, come Spring I always plant seedlings on window sills and plan out gardens, which is the same, but WHAT I plant and where changes, thus my 'sweet spot'.
IN work (mine being an artist) this is similar. My studio often goes through various arrangements as it gives one the 'feeling' of control over environment and a look of 'change' within the stability of routine.
Well thought out @chbartist